The present invention relates to flat carding machines in which a thin layer of fibrous material is processed in a plurality of stages passing between the surfaces moved by relative motion and provided with clothings of points or needlesxe2x80x94moved by relative motionxe2x80x94encountering cleaning blades and suction outlets. In these stages the fibrous material in flock is opened out and purified, the smallest particles of dirt are eliminated, as are waste and tangles. During carding the fibres are homogenized to form a blend with one other; the carded product is composed of a sliver of fibres essentially paralleled, to be sent to the subsequent stages to produce yarns.
To illustrate the problems and difficulties of the carding operation, confronted in the present invention, the work of a flat carding machine is schematically described with reference to FIG. 1.
The raw material 1, composed of fibres in a layer of flock, is fed to the carding machine by a feeder roller 2 that, with the opposite board 3, supplies a wide tuft 4 to the taker-in cylinder 5, currently named xe2x80x9cbriseurxe2x80x9d. Said briseur is provided with a clothing of points, generally less dense than those of the carding cylinder, and rotates at considerable speed; the fibres of the tuft 4 are distributed on the clothing of the briseur and are roughly combed and disentangled. Along their path on the briseur, the fibres encounter fixed segments with point clothing and blades to remove impurities and then pass on to the subsequent carding cylinder 6. This carding cylinder is, in fact, operated at a higher peripheral speed than the briseur speed and its points remove the layer of fibres, at their nearest generatrices. In general, the carding cylinder 6 is provided with a denser and more minute clothing than the briseur.
The travelling flats 7 are positioned in line with the upper part of the cylinder 6. These travelling flats are bars with a useful length corresponding to the width of the cylindrical surface of the carding cylinder 6 and a few centimetres in width. The part of them that faces the clothed surface of the cylinder 6 is also provided with a clothing of points. Generally, the travelling flats move at low speed in the same or in the opposite direction to the cylinder motion, which instead moves at noteworthy speed. The respective clothings opposite one another perform the typical carding action of distending and cleaning the fibres. The peripheral speed of the cylinder generally ranges from 15 to 40 metres per second, while the speed of the flats is in the order of a few centimetres per minute.
The flats 7 thus circulate around an arc of the periphery of the cylinder 6 operated by a drive element 8, for example chains or toothed belts, which circulate in a closed circuit between a series of actuating and guiding toothed wheels 9. Along the carding path between the cylinder and the flats, the flats are guided by guides 10 that are regulated with extreme precision, to determine the reciprocal distances between the clothing of points of the cylinder and of the flats, which are essential for the efficacy and quality of processing. The guides 10 are positioned in line with the edge of the flat faces of the cylinder and are grazed by the end parts of the flats 7, not fitted with points. The distended and cleaned fibres on the carding cylinder 6 are then removed by a doffer 11 and removed from this with detaching cylinders not shown in the figure.
In the traditional art, the bodies of flats are generally made of cast ferrous material, typically cast iron, subsequently fitted with the clothing of points for carding. These traditional flats are generally driven by articulated pulling chains to which the flats are fixed, both in the articulations and plates of the chain, with elements known to the state of the art.
In order to simplify and lighten the device, more recently designed carding machines use travelling flats produced by a section bar, subsequently fitted with carding clothings. These flats, generally made from T-bars with lightening cavities, while satisfying the requirements for stability and flexural and torsional rigidity, are lighter and altogether less expensive. Generally, lighter materials, such as light aluminium alloys, are used to make these lighter flats and drive is provided with toothed belts in place of traditional metal chains.
More information on the state of the art of carding machines and travelling flats is found in the European patent application EP-A-361.219 by Truetzschler GmbH, and in the European patent application EP-A-567.747 which describes the insertion, into the ends of the carding flats, of cylindrical pins more resistant to wear to rest these on the guides 10. European patent application EP-A-627.507 by Maschinenfabrik Rieter AG describes a coupling between the carding machine flats and the toothed drive belt using the same pins to rest on the guides 10. European patent applications EP 794.271 and 794.272 in the name of the applicant, describe further systems for connecting the card to the toothed belt, envisaging the use of coupling pins between the toothed belt and the flats and separate from the pins with which the flats rest on the guides.
There is a problem with technical solutions according to prior art in that when carding on the main cylinder, noteworthy impurities accumulate caused by foreign materials contained in the flock fibre fed to the carding machine, such as sand, dust, short fibres, neps and so on. These materials produce significant deposits that stratify on the guides 10.
These deposits adhere to give rise to noteworthy problems. For example, the distance set between the clothings of the carding cylinder and of the flats is modified and influences the efficacy of processing proportional to the distance with which the flat follows the direction of the profile of the guides 10. Another problem is caused by the abrasive action that this layer of material deposited on the guides 10 exerts on the pins on which the flats rest and in particular on their generatrix in contact with the guides. Due to this wear, systematic maintenance is required on the majority of the flats to restore the pins and adjust the distances between the clothings.
The object of the present invention is to provide a system to remove the deposits of foreign material on the guides 10 with which these are essentially contrasted, if not totally eliminated.
The device according to the invention is defined in its essential components, in the first claim, while its variants and preferred embodiments are specified and defined in the dependent claims. From the exemplificative description ensuing, the travelling flats assembly activated to slide on the guides 10 is provided, in its overall development, with scraping or cleaning elements that come into contact with the surface of the guides 10, removing the deposit of foreign material from the surfaces of the guides 10, on which the elements on which the flats rest are pulled, in any case contrasting accumulation.
To illustrate the characteristics and advantages of the present invention with greater clarity, it is described with reference to some typical embodiments shown in FIGS. 2 to 6, provided as non-limiting examples.
Said figures refer to the flat/guide system according to the invention and also to various examples of embodiment of said scraping or cleaning elements, to illustrate the characteristics and benefits ensuing from the present invention. The exemplificative illustrations below refer to the model of carding machines with travelling flats driven with a toothed belt, it being specified that the present invention is not limited to the use of this type of drive element.